1. Field of the Invention
This invention relates generally to mooring systems for offshore floating terminals. In particular, the invention relates to an apparatus and method by which a steel catenary riser is connected to a turret of a floating storage and/or production vessel while simultaneously fluidly coupling the riser to a flowline in the turret.
2. Description of the Prior Art
Flexible riser hang-off systems have been proposed for hanging off Steel Catenary Risers (SCRs) from offshore terminals. FIG. 1 of the attached drawings shows a typical prior art receptacle/flexjoint assembly 10 for an SCR 12 where a xe2x80x9cflexjointxe2x80x9d (a proprietary product of Oil States Industries Inc.) assembly 11 is hung off the side 14 of a production platform by a receptacle frame 13. A sealed fluid coupling between riser 12 and a platform flowline 7 is accomplished. Other prior art riser hang-off assemblies 10A, 10B, 10C with pull-in hardware 16 are illustrated in FIGS. 2 through 4. FIG. 2 shows a prior art hang-off arrangement known as a LYNX(trademark) system. An I-tube 60 is mounted in an opening of a mono-buoy structure 150. A pull in head 16 is secured to a frustro-conical shaped connecter 8 and flex joint 11A secured to the top of the riser 12. A sealed connection is made at I-tube seal 9, when the riser is pulled up into the I-tube 60.
FIG. 3 shows another prior art hang-off arrangement where a riser 12 is pulled alongside a platform 14 for sealed fluid connection to a platform flowline. The arrangement of FIG. 3, known as an Alligator Rigid Riser Pull-on System, also includes a flex joint assembly 11A, a pull-in head 16 and coupling devices for sealingly coupling riser 12 to a platform flow line.
FIG. 4 shows a prior art hang-off system known as a hydraulic rigid riser pull-in system, also having a flex-joint assembly 11B, a pull-in head 16 and an arrangement for providing a sealed connection between the riser 12 and flow lines of the structure.
While flexible riser hang-off systems such as 10, 10A, 10B and 10C have been proposed for production platforms, a problem remains for pulling in and connecting SCRs to flowlines of a turret of an offshore terminal such as a Floating Storage and Offloading vessel (FSO) or Floating Production Storage and Offloading vessel (FPSO). The problem concerns connection of the Steel Catenary Riser to the flowline within the mooring turret without costly and dangerous intervention by deep sea divers.
3. Identification of Objects of the Invention
A primary object of the invention is to provide a method and apparatus for connecting a SCR to a flowline within a turret of a FSO/FPSO that will minimize intervention by divers.
The object identified above, along with other features and advantages of the invention, is embodied in an arrangement with a flexjoint and a hydraulic connector hung from the bottom end of the turret and fluidly coupled to production piping (e.g., a flowline) within the turret. A pull-in line run through the production piping, flexjoint and hydraulic connector, includes a riser pull-in head which latches to a riser connector hub installed in the upper end of the riser. In operation, the pull-in line pulls the riser (SCR) to the hydraulic connector for operational securement to the end of the turret flowline.